Energy from wine-growing waste

Vineyard in Rheinhessen

Electricity and heat can be generated from old vine wood and pomace. © A-Tom/ iStock

The truth lies in wine – and there is enormous energy potential in the remains of wine production. This organic waste from crushed grape skins or old vine wood could be burned to provide electricity and heat for wineries and households. Researchers have found that Germany’s wineries could generate a total of around 4.2 petajoules of usable energy in this way. That corresponds to the annual electricity consumption of 47,000 single-family homes.

Large quantities of waste products are produced every year in wine production, including pomace – the solid to pulpy residue after pressing the grapes – and the vine wood that remains after the vines have been cut. At present, most of the pomace is still used as fertilizer or processed into brandy, which is how Italian grappa is made, for example. The vine wood, on the other hand, is usually uselessly burned in so-called “bonfires”.

Straw bale gasifier for heating vine wood

A research team from the Technical University of Cologne has now developed a concept for the energetic utilization of wine residues. To do this, the researchers developed a device that is usually used to burn straw bales so that it can also burn vine wood and pomace instead of dry grass. When the wine residues are burned, heat is generated that can be transferred to surrounding water pipes via a heat exchanger. The combustion heat could also be converted either into useful cooling via an absorption refrigeration system or into electricity via a hot gas turbine.

Based on the quantities of vine wood and pomace in two selected wineries, the researchers use simulation software to estimate how much energy the combustion of wine residues could provide per winery. “With this concept of using biomass waste such as vine wood and pomace instead of conventional fuels such as natural gas and heating oil, it would be possible to generate energy for the specific needs of wineries,” explains Felipe Torres from the TH Köln.

Enough energy for 47,000 single-family homes

Based on their data, the researchers determined how much energy could be generated across Germany using this technology. To do so, they used the following basic assumptions: According to the Federal Ministry of Food and Agriculture, Germany’s large wineries produced a total of around nine hundred million liters of wine in 2020. Around 250 grams of pomace are produced per liter of wine – this equates to 230,000 tons of pomace. In addition, around 308,000 tons of vine wood are produced every year.

From this it is possible to calculate how much energy is released when this wine-growing waste is burned. “In total, 4.2 petajoules are available from the residual biomass of pomace and vine wood,” reports Torres. This corresponds to the annual electricity and heat requirements of more than 47,000 single-family homes. And even if the wineries continued to use the 230,000 tons of pomace at least partially for fertilizing or to produce spirits, even the burning of vine wood alone would provide almost 2.8 petajoules of energy annually.

“In the German wine-growing industry, conventional fuels such as natural gas and heating oil are predominantly used to operate the technical systems for producing and cooling the grape juice. However, large quantities of organic residues are produced in the growing areas in particular, which could provide energy with lower emissions,” says Thomas Mockenhaupt from the Cologne University of Applied Sciences, summarizing the results. In addition, the remaining ash could be used as fertilizer in the vineyard. According to Mockenhaupt, this complete utilization of the residues on site would be a successful example of the circular economy.

Source: Cologne University of Applied Sciences

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